We will characterize the alteration in rat liver Hyperplastic Nodule epoxide hydrase compared to normal epoxide hydrase by: Purification of each enzyme followed by amino acid analysis, SDS-PAGE analysis of cyanogen bromide cleavage polypeptides, tightly associated lipids, glutathione-mixed disulfides and carbohydrate. We will investigate if activated carcinogen is bound to epoxide hydrase from normal liver, or hyperplastic nudule, both in vivo and in vitro. We will study dissociation of nodule or normal epoxide hydrase from their respective microsomal membranes, since the hydrase from nodules appears more loosely bound. Cholesterol epoxide will be tested as substrate for both type enzymes, and these studies will also be extended to hepatoma. Cholesterol expoxide will be tested as substrate for both epoxide hydrases, normal and abnormal. Cholesterol epoxide and its presumed product, cholastan 3 beta, 5 alpha, 6 alpha-triol will be quantitated in normal, nodule and hepatoma microsomes by extraction, thin-layer chromatography and gas-liquid chromatography.